Lift truck mechanism



United States Patent Harold A. Stammen Bremen, Ohio Feb. 17, 1969 Dec. 1, 1970 Crown Controls Corporation New Bremen, Ohio a corporation of Ohio inventor Appl. No. Filed Patented Assignee urr TRUCK MECHANISM 9 Claims, 4 Drawing Figs.

US. Cl. Int. Cl. Field of Search [56] References Cited UNITED STATES PATENTS 2,636,768 4/1953 Hansen 214/653X 3,223,267 12/1965 Stammen... 214/730 3,235,105 7 2/1966 Loomis 214/731X Primary Eimminer-Gerald M. Forlenza Assistant Examiner-Robert J. Spar Attorney-Marechal, Biebel,-French and Bugg ABSTRACT: Mechanism for controlling the sidewise movement of fork lift tines includes symmetrical bell cranks mounting the tines for swinging movement, a support member carrying the cranks and vertically movable on a carriage part, and a track on the carriage part engaging rollers on the cranks to translate relative vertical movement of the support member and carriage part into swinging motion of the cranks.

Patented Dec. 1, 1970 INVENTOR HAROLD A. STAIIMEN ,M,Mjfllg nrromvsrs I LIFT TRUCK MECHANISM BACKGROUND OF THE INVENTION This invention relates to lift truck mechanisms, particularly to forklift trucks which have pivoted swinging tines. A typical device of this type is disclosed in Stamrnen US. Pat. No. 3,223,267, issued Dec. 14, 1965 to the assignor of this application. This movable tine arrangement is particularly useful in handling baskets and the like which carry bulk loads, for example the type of basketcommonly used to support a quantity of tobacco leaves.

In the construction shown in the aforementioned patent, the fork tines are biased to an outerposition by springs, and the lift mechanism is attached directly to the cranklike'brackets from which the tines extend. Pivot mountings for the brackets are arranged such that with the mechanism fully lowered, initial operation of the lift mechanism causes the tines to swing,

against the spring force, downward and inward under the basket until the pivoting brackets reach a stop, then the carriage and forks lift together.

In another type of device of this general character, the pivoting brackets swing downward and inward under their own weight as the carriage is raised, but this requires that'the brackets have rather substantial weight in order to accomplish this function when handling heavier loads. This type of action relies on gravity to position the tines for lifting, and any accidental interference with movement of one of the tines could result in the load being tipped over. Hence the. arrangement is unsuitable in situations where a load such as a basket is to be picked up from a floor or the ground.

SUMMARY OF THE INVENTION The present invention provides an improved forklift mechanism with swinging tines, which may be incorporated in specially constructed lift trucks, or which may be provided as an attachment to standard lift trucks having a lift carriage on which various accessories can readily be mounted. A carriage part is adapted for attachment to the liftmechanism,such as its standard carriage, and in turn mounts a support member which is vertically'movable on the carriage part to a limited extent. A pair of symmetrical crankmembers are pivoted to the support member, and the movable tines project forwardly from the generally vertical leg of the cranks, while the generally horizontal leg of each crank is provided with a roller engaged in a horizontal track on the carriage part. Preferably the support member also has casters fixed to its bottom for engaging the ground when the mechanism is fully lowered.

When the lift mechanism raises the truck carriage, the carriage part first moves upward and its track causes the rollers on the cranks to swing upward, thereby swinging the tines positively and together, downward and inward beneath a basket or other load, after which the cranks reach limit stops on the support member, and it and the carriage part then rise together. When the load'is being deposited, the casters engage the ground surface, halting the lowering movement of the support member, and the carriage part continues to lower'with the track and rollers then causing anoutward and upward swinging movement of the tines from beneath the load.

The object of this invention, therefore. is to provide a novel lift truck mechanism for-incorporating inward and outward moving fork tines, including a simplified arrangement for positively actuating the movement of the tinesyparticularly when bringing the tines inward beneath a load fora lifting operation; and to provide such a mechanism which can'readily beincorporated in a lift truck especially adapted for use with this mechanism, or can be provided as an attachment for mounting on standard lift trucks.

Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of the improved forklift mechanism with movable tines, showing the carriage in its lowermost position and the tines swung to their outward position;

FIG. 2 is a perspective view showing the lift mechanism partially raised and the tines moved to their inner position preparatory to lifting a load;

FIG. 3 is a top view, with portions of the tines broken away, showing details of the mechanism; and

FIG. 4 is a vertical sectional view, with the ends of the tines broken away, showing the manner in which the mechanism can be mounted on a standard lift truck carriage DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, particularly to FIGS. 1 and 3, the novel mechanism'provided by the invention includes a carriage part 10 provided with-suitable mounting brackets 12 by means of which it can be attached to conventional lift mechanism, for example a standard lift carriage, as later described. At the opposite sides of the carriage part 10 there are vertically extending tracks 14 which form a mounting for a support member indicated by the general reference numeral 15. This support member includes a lower crossbar 16, side pieces 17, and inward extending top bars 18 which are supported at their inner ends by vertical reinforcing bars 19 projecting upward from thebottom crossbar 16. The side pieces 17 have rollers.20 mounted'thereon and extending into the tracks 14, thus the entire support member and carriage-part are vertically movable with respect to eachother. This move ment is limited, as will be described, to prevent the parts becoming disengaged.

Extending forward from each of the upper bars 18 are pivot pins 22 which define pivot mountings for L-shaped bellcranks or brackets. These cranks are symmetrical in construction, and the left side crank, in FIG. 1, is indicated at 250, the right side crank at 25b. Each crank includes a generally horizontal arm, 26a and 26b, and a generally vertical arm 27a and 27 b. The tines 30a and 30b of the fork mechanism are secured to the lower ends of the vertical arms 27a and 27b and extend generally forward of the mechanism.

Brackets 32a and 32b are fastened to the vertical bars 19. and surround the horizontal arms 26a and 26b of the cranks. Immediately behind the horizontal arms of the cranks, fixed to the upper portion of the carriage part 10, there is a horizontallyextending track 34.'Rollers 35a and 35b (F1653) extend from the crank arms 26a and 26b respectively, into this track, hence relative movement between the carriage part 10 and the support member 15 will produce swinging motion of the cranks, and thus move the tines toward or away from each other. The lower ends of the brackets 32a and 32b provide lower stops limiting the downward movement of the horizontal crank arms 26a and 26b. At the top of each of these brackets are adjustable stop bolts 37a and 37b, which limit the upward swinging movement of these crank arms. These upper stops need not be adjustable, although it is advantageous to be able to provide some adjustable inner limit of the tine motion.

As'shown in FIG. 4, the brackets 12 are arranged'to engage about a standard lift truck carriage 40, to which the chains 41 (FIG. 1) of a conventional lift mechanism are attached. The carriage 40 is mounted for vertical movement along the lift truck mast 42, under the control of any suitable power source such as the hydraulic cylinder 43. Details of this lift mechanism will vary with different types and styles of trucks.

As shown in FIG. 3, the carriage part 10 is in its lower position with respect to the support member 15, and the tines are spread apart. In this condition the truck is driven (if it is selfpropelled) or pushed into a position with the tines extending along opposite sides of a load, such as the basket 45 (FIG. 2) As the lift mechanism is raised, the carriage part 10 moves vertically upward with respect to the support member 15, and through the action of the drive connection between the track 34 and rollers 35a, 35b, the cranks are rotated in opposite directions, bringing the tines inward toward each other, and somewhat downward, beneath opposite sides of the load. The sides of the tines may be beveled to provide a wedging or cam action which assists in getting the tines properly placed beneath the load.

Once the crank arms 26a, 26b engage the stops 37a, 37b,

relative motion between the carriage part and the support member stops and the two are lifted together elevating the load for transporting purposes.

When it is desired to deposit the load in a given location, the lift mechanism is lowered until the support member reaches its lower limit. This may be provided by a suitable stop on the truck structure, or preferably by projections from the bottom of the support member 15 which engage the ground surface and terminate the lowering movement of the support a member. In a preferred arrangement casters 47 are mounted on the bottom of the lower crossbar 16 to perform this function. The carriage part 10, and the parts to which it may be attached in the lift mechanism, continue to lower, primarily under their own weight. By this time the center of the load, or at least portions of it, are resting on the ground surface, and some of the weight is relieved from the tines. As the carriage part 10 continues to lower, the aforementioned drive connection will operate in reverse to swing the cranks in the opposite direction and move the tines away from each other in an outward and somewhat upward direction, returning to the position shown in FIG. 1.

It should be understood that this movable fork mechanism can be constructed as a part of a specially adapted forklift truck, or this mechanism can be provided as an attachment. In one embodiment of truck, a counterbalanced lift truck construction which is generally well known is utilized, therefore forward extending outriggersare not required. This in some cases improves the maneuverability of the unit, and may be desirable where the total width of the mechanism is a limiting factor, since any outriggers of necessity must extend beyond the sides of the tines and clear of their paths of movement. The construction is, however, suitable for use with outrigger equipped trucks in the event that this type of structure should be desired for particular applications.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited. to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention.

lclaim:

1. Lift truck mechanism comprising the combination of:

a vertically movable carriage part having power-operated means for raising said carriage;

a support member mounted on said carriage part for limited vertical movement with respect thereto;

spaced cranks having spaced apart individual pivot connections to said support member;

a load supporting tine projecting outwardly from each of said cranks arranged for swinging movement about said pivot connections; and

a drive connection between each of said cranks and said carriage part arranged to swing said tines inward with respect to said support member as said carriage part is raised with respect to said support member and to swing said tines outward when said carriage part is lowered with respect to said support member. 2. A lift truck mechanism as defined in claim 1, said drive connection including:

an upper arm on each of said cranks extending toward the center of said support member from the corresponding pivot connection; a horizontally extending track on said carriage part; and rollers on each of said upper crank arms engaged in said track. 3. A lift truck mechanism as defined in claim 1, ground engaging means on the bottom of said support member defining the lowermost position of said sup ort member and providing for movement of said carriage par downward with respect to said support member and consequent outward movement of said tines.

4. A lift truck mechanism as defined in claim 3, wherein said ground engaging means are casters mounted on the bottom of said support member.

5. A lift truck mechanism as defined in claim 1, including adjustable stops on said support member limiting the rotation of said cranks in the direction of inward tine movement.

6. A lift truck mechanism as defined in claim 1, wherein said carriage part is constructed and arranged for attachment to a lift truck carriage.

7. Lift truck mechanism comprising the combination of:

a vertically movable carriage part;

a support member mounted on said carriage part for limited vertical movement with respect thereto;

cranks having horizontally spaced apart individual pivot connections to said support member near the top thereof;

said cranks each having a generally horizontal arm extending from the corresponding pivot connections toward the centerline of said support member;

said cranks each also having a generally vertical arm extending downward from the corresponding ivot connection;

a load supporting tine projecting outwardly from each of said vertical arms and arranged for swinging movement about said pivot connections toward and away from each other; and

a drive connection including a roller on each of said horizontal arms and a track on said carriage part arranged to swing said tines inward toward each other as said carriage part is raised with respect to said support member and to swing said tines outward and away from each other when said carriage part is lowered with respect to said support member.

8. A lift truck mechanism as defined in claim 7, including means on said carriage part adapted for attachment to the lift carriage of a lift truck.

9. A lift truck mechanism as defined in claim 7, including stops arranged to limit motion of said horizontal arms as said tines swing toward each other. 

